Receptacle contacts are known which have a pair of opposing contact arms extending forward from a main body portion between which is insertable a male or plug terminal. The contact arms act as spring members and tend to converge first toward each other to a closest point and then diverge forming a lead-in for a plug terminal. At the closest point the contact arms are at a distance from each other less than the width of the plug terminal so that when the plug terminal is inserted between the contact arms, the contact arms are forced apart by the plug terminal, but because of their spring nature the contact arms maintain a contact force against the plug terminal and thus maintain electrical engagement therewith. Generally, the greater the contact force, the better the integrity and quality of the electrical engagement, but necessitating higher insertion force.
Especially in power-conducting terminal connections, high quality electrical engagement is critical and is dependent not only on high contact force but also upon the use of high grade conductive metal such as alloys having high copper content. Contact arms made from such alloys have relatively low resilience because of the low yield stress of copper. As a results, receptacle contacts of such metal have contact arms which do not have strong spring characteristics and thus do not provide high contact force against the plug terminal.
One particular prior art method of compensating for low resilience in the contact arms of a receptacle contact was the use of an anti-overstress spring which straddled the base sections of the contact arms, had arm sections coextending along the outer surfaces of the contact arms to their inward-most point. Then the arm sections of the spring were doubled back for some distance before ending; such doubled-back sections were designed to engage the sidewalls of the housing cavity in order to provide support to the contact arms near the forward ends of the contact arms which increased the contact force of the contact arms against the plug terminal inserted between the contact arms. Such an arrangement relied heavily on the cavity walls retaining a definite width dimension, and because of heat buildup in the housing this dimension changed due to expansion of the housing material making the performance parameters of the anti-overstress spring variable and thus unreliable.